Spiral contactor for solvent extraction column



June 13, 1961 SPIRAL CONTACTOR FOR SOLVENT EXTRACTION COLUMN C. R. COOLEY Filed Deo. 24, 1958 vlllllll INVENTOR. Caf! j?. Cool@ 2,988,429 SPIRAL 'CONTACTOR FOR SOLVENT EXTRACTION COLUMN Carl R. Cooley, Richland, Wash.,.assignorto the United States of America as representedby the'UnitedStates Atomic EnergyCommission Filed Dec. 24, 1958, Ser. No. 782,983 2 Claims. (Cl. 23-2705) This invention relates to the removal of materials, such `as metal Nvalues or impurities, from a liquid bymeans of another liquid brought into intimatecontact with the first liquid and then separated therefrom. More specifically, ythe invention relates to counter-current extraction in a pulse column.

When radioactive materials are being .acted upon, height of the column becomes of great importance because of the cost oi shielding. Therefore itis important to reduce height of a column as much aspossible while maintaining the eiciency of the column.

An object of the present invention is -to shorten an extractioncolumn Without loss in efficiency. This .object 'is laccomplished by making the liquids follow :a -non- -linearpath'that is longer than the` ordinary straight path of the liquids lengthwise of the column.

. According to the presenti invention, the V extraction* column is provided with a spiralfribbon formed' in sections extending lbetween perforated plates -and yfrom Vthe'in- .terior ofthe .column wall-.to -a commonncentenpost to -Which the sections .are `secured` for support.

Other 'objects willlbe=apparent-from the followingfdescription and drawings in'which:

FIG. l'is a diagrammatic view of-.the -mixer-settlerA of the present invention; and

FIG. 2 is a sectionalview of-a .portion of-the extractioncolumn of `the mixer settler with its novel-spiral ribbon.

`In the casein which'the organic phase influent has a lower densitythanfthe aqueous phase influent, the apparatusof the present-.invention comprises Va hollow cylindrical column 10,aninlet line l-lfor-aqueousfphase at `the'top of the column, an outletzlineflZfor the organic phase `atthe .topof the column, anlinlet line =13 .for the organicphase at the bottom fof thecolumn, anou-tlet'line 14 for the aqueousgphase at thebottomof the-column, .a motoreoperated bellows 115 for supplying pulses to :liquid inthe columnpanda pluralityy of perforatedplates 16 extending acrossthe .col-umnzin spaced relation-tonne another.

The present I apparatus also has, "asua Inovel 'feature, a spiral element 17 which extends along the column 10 throughout the'region` occupied-"bythe `peiforated pl-ates :16 andi increases the length ofthe:countercurrentjcontact :between the phases in the column bymaking themfollow --a spiral, path. Y

As shown in FIG. 2, the perforated plates 16 are held in spaced parallel relationship by being clamped between short tubular sections 18 mounted on a rod 19 extending along the axis of the column 10. The spiral element 17 comprises a plurality of spiral radial ribbon sections 20, each of which is welded or soldered at its inner edge to a tubular section 18 and has its outer edge immediately adjacent the inner surface of the column 10. The tubular nite States Patent sections 18 and the rod 19 extending through them may be considered to comprise a center post 21 to which the Vribbon element 17 is secured. Each spiral section 20 extends from one perforated plate 16 to an adjacent plate V16. In the arrangement in.FIG.2, the end of each section 20 is spaced from the adjacent endV of the next section by the perforated plate 16 lying between the two sections 20 and these ends of the two sections are generally coincident with one another, so that the spiral element 17, formed by the spiral lsections `18, -is generally continuous, being interrupted only by the perforated plates v16. The ribbon sections 20 may be heldagainst rotational shifting by endwise clamping of the tubular sections 18 and the perforated plates 16.

In experiments carried out to test the inclusion of the spiral element 17 in the above apparatus, the column 10 had an internal diameter of 3". Correlations weresought for the prediction of spiral-cartridge performance from the performance of a standard cartridge or, in other Words, a cartridge with the same hole diameter for the .perforated plates 16, percent free area therein, and distance therebetween, but withoutthe spiral element `17. For thepurpose of the experiments, the column 10i had near a midpoint in its-length, an outletline 22for the `aqueous phase.

Definitions of terms used Cartridge-A longitudinal section of the apparatus comprising a perforated plate l16 Aand the portion of the eolumn 10 extending between the saidplate 16 and the next Percent free area-That percent of the area of an equilateral triangle formed' by connecting hole centers in the perforated plates 16, `which is open because of the s holes.

Pitch-The distance measured axially of the column V10 required for the spiral element 17 to go completely about the center post 21.

lAmplitude-'Thevertical displacement of liquid within the column -10 measured fromaone extremity in a given cartridge-to the other extremity in the same cartridge or in the cartridge belowvthe Igiven cartridge.

"Flooding frequency-That frequency at which-sufficient .organic phase is rejected'fromfthe bottom of a cartridge to `form an interface While =the top interfacezposition is maintained by adjustment of thebottom effluent stream. Colburn Transfer Units-HTU, ft.-"The height-ofa `transfer unit in feetxas explained lin Industrial .and Engineering Chemistry, vol. T33, No. 4, Lpages '459-467, April l1941. `'I'hus the height toffafcolumn :is '.'obtained' Vthatis required forza givenmassitransfer.

Efficiency-The Irelative ability `:of 21a given extractor v column to; perform-f a givenffextraction. 'asiindicatedztby the "HTU values column is agreater,.when:.the. H"l?U1vaiue:and,"thereby,ithe

The improvement, obtained vwithi the new MASS TRANSFER STUDIES-SPIRAL PULSED COLUMN CARTRIDGE Stream Analysis, Average grams/liter I Pulse (Efficiency) Pulse Freq., Nom. Act. Aq/Org. Colburn Run Amplicycles Vol. Vel., Vol. Flow Org. Aq. In Middle-Aq. Bottom-Aq. Org. Pitch, in. Transfer No. tude, In. per gaL/hr.- Vel. Ratio In Out Out Out Unit HTU, min ft.:4 ft. Top 3 it.

U U HN 03 U HN 0a U HN O3 U 1 44 70 500 487 411 .95 11.15 17. 4 U96 14 4. 2 3 66 2 .6 70 500 539 .407 .1 11.15 17.4 4. 7 N0 spiral.. 81 3 35 70 500 524 .428 .039 11.3 18. 0 5.0 2 .73 4 5 65 500 507 .395 O11 11.2 21.1 4. 25 6 67 5 .44 65 500 529 .381 .019 11.25 19.6 4. 4 3 i 50 6 .6 65 500 513 375 0058 No Spiral- .67

From the above table it is concluded that the efficiency of a spiral cartridge is 25% better than the eiciency of a standard cartridge. A spiral pitch of 3 to 4" gave the optimum efficiency in the column 10 with an 4in-ternal diameter of 3". Spiral pitches of 2", 3", and 6 were compared to the standard cartridge. In each case the perforated plates 16 were 2" apart and had a hole diameter of lz" and a 23% free area.

From these tests and other tests made but not reproduced here, it is concluded that:

Capacity of a spiral cartridge was equal to the capacity of a standard cartridge if the pulse amplitude in the spiral cartridge was l2 to 42 percent less than the amplitude in the standard cartridge.

Pulse amplitude (0.26 to 1.5 inches), flooding frequency (40 to 120 cycles per minute), sieve plate spacing (2 to 4 inches), sieve plate free area (10 to 42 percent), sieve plate hole diameter (1/16 to 5% 6 inch), spiral pitch (2 to 6 inches) and aqueous to organic flow ratio (0.2 to 2.0) were studied. Increasing sieve plate spacing, hole diameter, or percent free area gave similar increases in capacity for the standard and the spiral cartridge. Decreasing spiral pitch decreased capacity for the same pulse amplitude. Changes in aqueous-to-organic ow ratio did not change capacity.

Pulse amplitude, iiooding pulse frequency, and Volume velocity were tested in a spiral cartridge and a standard cartridge. Perforated plates 16 were spaced two inches apart and each had a hole diameter of Vs inch and a 23 percent free area. Capacities or flooding frequencies of the spiral cartridge were approximately equal to the flooding frequencies of the standard cartridge if the spiral cartridge vertical amplitude was 58, 78, and 88 percent of the standard cartridge vertical amplitude for a spiral pitch of two, three and six inches, respectively.

Changing the plate spacing from two to four inches produced a 30 percent increase in the flooding frequency of a spiral cartridge at a volume velocity of 800 gal/brit?. The flooding frequency of the standard cartridge was increased percent for the same conditions. Changing the plate spacing from two to four inches did not change the flooding frequency of the spiral cartridge or the flooding frequency of the standard cartridge at a volume velocity of 200 gal./hr.ft.2.

A change in sieve plate hole diameter from 1,46 to V16 inch did not change the flooding frequency of a spiral cartridge with a three-inch pitch. Volume velocities were 200 to 800 gall/hr. ft2. Free Iarea of the sieve plates was 23 percent for all hole diameters. Plates were spaced two inches apart. Increasing the hole diameter from 1/16 to 1%@ inch produced a 20 percent increase in the flooding frequency of a standard cartridge at a volume velocity of 800 gal./hr.ft.2.

Increasing the free area of the sieve plates from 10 to 23 percent exhibited up to a 50 percent increase in flooding frequencies for both a standard cartridge and a spiral cartridge with a three-inch pitch. Hole diameter of the sieve plates was 1A; inch; spacing of the sieve plates was two inches. Changing the free area of the sieve plates from 23 to 42 percent produced up to a 25 percent increase in the flooding frequency of both the spiral cartridge and the standard cartridge.

In the present case the spiral pitch cannot be less than about 2" because of the tendency of spiral channeling, that is, the gross countercurrent bypassing of aqueous and organic emulsion due to the riding of the organic phase on the spiral element 17. The disadvantage of unduly increasing the pitch of the spiral element 17 is, of course, apparent; there is no real reduction in the'length of the column 10.

The intention is to limit the invention only Within the scope of the appended claims.

What is claimed is:

l. A pulsed-column extraction apparatus, comprising a column, a plurality of equally spaced at perforated plates perpendicular to the wall surface of said column each covering the cross-sectional area of said column, an organic-phase-ingress line and au aqueous-phase-egress line at one end' of said column, an aqueous-phase-ingress line and an organic-phase-egress line at the other end thereof, liquid pulse means connected to said column, and an imperforate spiral ribbon along the length of said column, whereby the length of the path of the liquids is increased, said spiral ribbon being formed of spiral sections, each section of the ribbon extending only the distance between two adjacent perforated plates.

2. The apparatus of claim l, and further comprising a center rod extending through the column, said perforated plates being mounted on said rod, a plurality of short tubular sections mounted on the rod and extending between the perforated plates, the spiral sections being secured at their inner edges to the tubular sections, and having outer edges at the inner surface of the column.

References Cited in the file of this patent UNITED STATES PATENTS 2,628,894 Langmyhr Feb. 17, 1953 2,808,318 Feick Oct. 1, 1957 2,852,349 Hicks et al. Sept. .16, 1958 

1. A PULSED-COLUMN EXTRATION APPARATUS, COMPRISING A COLUMN, A PLURALITY OF EQUALLY SPACED FLAT PERFORATED PLATES PERPENDICULAR TO THE WALL SURFACE OF SAID COLUMN EACH COVERING THE CROSS-SECTIONAL AREA OF SAID COLUMN, AN ORGANIC-PHASE-INGRESS LINE AND AN AQUEOUS-PHASE-EGRESS LINE AT ONE END OF SAID COLUMN, AND AQUEOUS-PHASE-INGRESS LINE AND AN ORGANIC-EGRESS LINE AT THE OTHER END THEREOF, LIQUID PULSE MEANS CONNECTED TO SAID COLUMN, AND AN IMPERFORATE SPIRAL RIBBON ALONG THE LENGTH OF SAID COLUMN, WHEREBY THE LENGTH OF THE PATH OF THE LIQUIDS IS INCREASED, SAID SPIRAL RIBBON BEING FORMED OF SPIRAL SECTIONS, EACH SECTION OF THE RIBBON EXTENDING ONLY THE DISTANCE BETWEEN TWO ADJACENT PERFORATED PLATES. 